PURPOSE: To eliminate the need for monitoring a DMC for each coding processing by applying DMA (dynamic memory access) input only to an area designated in a RAM.

CONSTITUTION: An input output control section 63 outputting a control signal at data input output to/from an input output section 60, a counter 61 counting up sequentially a value corresponding to an address of a storage section 40 from an output of the above mentioned input output control section 63, a 1st storage means 64 storing the initial value of the counter, a 2nd storage means 65 storing the final value of the storage range and a comparison means 66 outputting a control signal to write the output of the 1st storage means 64 to the counter 61 when the content of the counter 61 and that of the 2nd storage means 65 are coincident, are provided, the content counted by a signal of the input output control section 63 and an output of the 2nd storage means 65 are compared and when the both are coincident, a control signal to input the output of the 1st storage means 64 is outputted to the counter 61.